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Subelement O
RADAR
Section 90
RADAR Theory
What is the normal range of pulse repetition rates?
  • 2,000 to 4,000 pps.
  • 1,000 to 3,000 pps.
  • 500 to 1,000 pps.
  • Correct Answer
    500 to 2,000 pps.

What is the normal range of pulse repetition rates?

500 to 2,000 pps.

The pulse repetition rate is how many pulses are created in a unit of time. The radar will turn on and off in its carrier frequency. The pulse is the number of on/off switching that the radar does per second.

Other wave bands are described as cycles per second, which is kind of like on/off switching per second. Same idea for sonar systems.

The pulse repetition frequency (PRF) has an inverse relationship with time. That is, 1 unit of time (second) divided by the PRF

\[\frac{1 }{\text{PRF}} = \text{ Time, (second)}\]

For more information, please see Wikipedia's Pulse repetition frequency.

Also see Radar Tutorial Eu for the article on Pulse Repetition Frequency (PRF)

Highly useful Unit Converter on Translator Scale site, for Radar Maximum Unambiguous Range and Pulse Repetition Frequency Calculator


Reference: Radar specifications and use are listed in the Code of Federal Regulations, Title 47 Chapter I Subchapter D
Part 80 - STATIONS IN THE MARITIME SERVICES

Since applicable regulations are in a number of places, please use CTRL-F and search on the word "radar" to look up applicable regulations.

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The RADAR range in nautical miles to an object can be found by measuring the elapsed time during a RADAR pulse and dividing this quantity by:
  • 0.87 seconds.
  • 1.15 µs.
  • Correct Answer
    12.346 µs.
  • 1.073 µs.

The RADAR range in nautical miles to an object can be found by measuring the elapsed time during a RADAR pulse and dividing this quantity by:

12.346 µs.

For the range in nautical miles, determine the time it took the signal to bounce and come back, and then divide the amount by 12.36. For range in kilometers, divide by 6.66.

Remember that the speed of light is 300 million meters per second, while in nautical miles it is approximately 161,784 nautical miles per second.

For well-illustrated explanation, please see Radar tutorial EU article on Range or distance measurement

For mathematical formulas, please see Tutorialspoint articles on Radar Systems - Overview and Radar Systems - Range Equation


Reference: Radar specifications and use are listed in the Code of Federal Regulations, Title 47 Chapter I Subchapter D
Part 80 - STATIONS IN THE MARITIME SERVICES

Since applicable regulations are in a number of places, please use CTRL-F and search on the word "radar" to look up applicable regulations.

Last edited by markadlerdallas. Register to edit

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What is the normal range of pulse widths?
  • .05 μs to 0.1 μs.
  • Correct Answer
    .05 μs to 1.0 μs.
  • 1.0 μs to 3.5 μs.
  • 2.5 μs to 5.0 μs.

What is the normal range of pulse widths?

.05 μs to 1.0 μs.

Please see Wikipedia's article on Pulse Width

Also see Alternative Wars site for the article Computing Radar Characteristics.

For well-illustrated info, please see Radar Tutorial EU site for the article on Minimal Measuring Range and Pulse Radar.


Reference: Radar specifications and use are listed in the Code of Federal Regulations, Title 47 Chapter I Subchapter D
Part 80 - STATIONS IN THE MARITIME SERVICES

Since applicable regulations are in a number of places, please use CTRL-F and search on the word "radar" to look up applicable regulations.

Last edited by markadlerdallas. Register to edit

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Shipboard RADAR is most commonly operated in what band?
  • VHF.
  • UHF.
  • Correct Answer
    SHF.
  • EHF.

Shipboard RADAR is most commonly operated in what band?

SHF

The Super High Frequency band is from 3 GHz to 30 GHz, which means that the waves are from 10 centimeters to 1 centimeter (10 cm to 1 cm). The SHF was defined by the International Telecommunications Union, ITU.

The SHF waves can transmit to approximately 60 miles. Due to its properties such as clearly identifying metal objects because of its reflection and the narrow wave simulating a beam, it is highly used in Radar technology.

For more info, please see Wikipedia's article on Super high frequency

Also see Copradar site for the tables of Radio and Radar Frequency Bands.

For an excellent and well illustrated overview of the use of frequency ranges, please see Radar Tutorial EU, for the article Waves and Frequency Ranges


Reference: Radar specifications and use are listed in the Code of Federal Regulations, Title 47 Chapter I Subchapter D
Part 80 - STATIONS IN THE MARITIME SERVICES

Since applicable regulations are in a number of places, please use CTRL-F and search on the word "radar" to look up applicable regulations.

Last edited by markadlerdallas. Register to edit

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The pulse repetition rate (prr) of a RADAR refers to the:
  • Reciprocal of the duty cycle.
  • Pulse rate of the local oscillator.
  • Pulse rate of the klystron.
  • Correct Answer
    Pulse rate of the magnetron.

The pulse repetition rate (prr) of a RADAR refers to the:

Pulse rate of the magnetron.

For more information, please see Wikipedia's article on Cavity magnetron

Also, see Radar Tutorial EU site for the very well illustrated article Magnetron

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If the elapsed time for a RADAR echo is 62 microseconds, what is the distance in nautical miles to the object?
  • Correct Answer
    5 nautical miles.
  • 87 nautical miles.
  • 37 nautical miles.
  • 11.5 nautical miles.

If the elapsed time for a RADAR echo is 62 microseconds, what is the distance in nautical miles to the object?

5 nautical miles.


From wp2ahg:

Light travels 186,000 mps, or 161,630 nmps.

If the radar signal was returned in 62 microseconds, then the distance to the target was reached in half that time, or 31 microseconds.

So, the distance to the target is
161,630 nmps x 0.000031 secs = 5 nautical miles


Reference: Radar specifications and use are listed in the Code of Federal Regulations, Title 47 Chapter I Subchapter D
Part 80 - STATIONS IN THE MARITIME SERVICES

Since applicable regulations are in a number of places, please use CTRL-F and search on the word "radar" to look up applicable regulations.

Last edited by markadlerdallas. Register to edit

Tags: none

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